Summary Pathophysiology Notes: Modules 1, 2, & 3

Pathophysiology Notes: Modules 1, 2, & 3 Module 1 Chapter 2: Homeostasis, Allostasis, and Adaptive Responses to Stressors Homeostasis & Allostasis Homeostasis: Remaining stable while staying the same A state in which allsystems are in balance A state of equilibrium An ideal “set point” despite alterations within the body Allostasis: Ability to successfully adapt to challenges Intricate regulatory processes orchestrated by the brain A dynamic process that maintains or re-establishes homeostasis in light of environmental and lifestyle changes Stress As A Concept Physical, chemical, or emotional factor resulting in tension of body or mind Actual physical and mental state that tension produces Real or perceived threat to homeostasis Direct consciously or indirect unconsciously sensed threat to the stability of the organism Physical, chemical, or emotional factor resulting in tension of body or mind Actual physical and mental state that tension produces Real or perceived threat to homeostasis Direct consciously or indirect unconsciously sensed threat to the stability of the organism General Adaptation Syndrome (GAS) (Selye) Three stages: Alarm,resistance/adaption, and exhaustion Alarm stage: fight-or-flight response asthe result ofstressfulstimulus ▪ Hypothalamic-pituitary-adrenal (HPA) axis Resistance/adaptation: activity of the nervous and endocrine systems in returning the body to homeostasis ▪ Allostatic state: activity of varioussystems attempting to restore homeostasis Exhaustion: point where body can no longer return to homeostasis ▪ Allostatic overload: “cost” of body’s organs and tissues for an excessive or ineffectively regulated allostatic response; effect of “wear and tear” on the body P. 16 Fig. 2-2; P. 15 Stressors Agents or conditionsthat can produce stress; endanger homeostasis ▪ May be external or internal • External examples:school, work, life event (wedding) • Internal examples: cancer, child birth/pregnancy ▪ Physical, chemical, biological, social, cultural or psychological • Physical: hand injury • Social:standing in front of a class • Cultural: acceptance/ability to practice ▪ Vary in scope, intensity, and duration ▪ Reactions to stress vary depending upon genetic constitution, gender, past experiences, cultural influences, developmental stage, and age • Past experience: a child afraid of a playground b/c he was previously abused there ▪ Can include both negatively and positively perceived events Risk Factors: Not stressors, but conditions or situations that increase the likelihood of encountering a stressor; there is some control over our stressors Neurohormonal Mediators of Stress & Adaption Catecholamines ▪ Play an integral role in allostasis ▪ Symphathico-adrenalsystem response mediatesthe fight or flight response ▪ Examples: Norepinephrine and epinephrine Norepinephrine ▪ Constricts blood vessels and raises blood pressure ▪ Reduces gastric secretions Epinephrine ▪ Enhances myocardial contractibility, increases heart rate, and increases cardiac output ▪ Causes bronchodilation ▪ Increase the release of glucose from the liver (glycogenolysis) and elevates blood glucose levels Adrenocortical Steroids ▪ Critical to maintenance of homeostasis ▪ May synergize or antagonize effects of catecholamines • Examples: Cortisol and aldosterone ▪ Cortisol • Primary glucocorticoid • Affects protein metabolism • Promotes appetite and food-seeking behaviors • Had anti-inflammatory effects • Too much cortisol over time can lead to pro-inflammatory effects ▪ Aldosterone (secreted by the adrenal cortex)